A tape drive head assembly generally comprises three main components: a magnetic read/write head, a movable carriage supporting the head, and a flexible circuit electrically connected to the head. The flexible circuit includes a fine positioner loop and a coarse positioner loop. A flexible printed circuit provides communication between the main control circuitry of the tape drive and the head positioning apparatus. Generally, a voice coil serves as an actuator for the fine positioner.
Magnetic tape data storage devices, or tape drives, are used for storing large quantities of computer data. As storage capacities of tape drives increase, the overall performance and structural integrity of the drives needs to improve. One of the areas needing improvement is found in the performance of the head positioning system.
Lateral motion at the read/write head needs to be controlled within a few micrometers in order to achieve a LTO (linear tape open) cartridge capacity of 400 GB, for example. Conventional techniques of controlling this lateral motion include a camming arrangement between a pivoting beam structure and the head structure that translates a rotational motion into a linear motion of the head traverse. The fine positioner prime mover is a rotary voice coil actuator. One of the major concerns with such an arrangement is the friction associated with both the pivot and cam follower systems. Unlike hard disk drives, a tape drive is an open system and subject to contamination. This makes pivot and cam-follower guide friction problems even worse. Further, there is a potential loss of accuracy during a rotary to linear motion conversion due to clearance in the cam-follower system, as well as wear in the pivot system. Thus, problems in servoing due to friction and the rotary to linear approach makes the requirement of controlling the lateral motion within two micrometers, for example, difficult to achieve.
Another concern of conventional head positioning systems is the lack of adequate structural rigidity in the coarse positioner construction to achieve a necessary frequency response requirement to perform adequate servoing. Conventional systems employ a single guide shaft, resulting in a cantilever beam with a low first mode of resonance. Due to this low first mode of resonance, it is difficult to maintain the required servo-bandwidth to satisfy the necessary accuracy requirement of high capacity tape drives.
Additional concerns with conventional coarse positioner constructions, which are required to hold the head carriage assembly and the voice coil system, include the inability to avoid structural problems of the voice coil holder structure, exacerbating resonance-related problems.
A still further problem with conventional coarse positioner constructions is the integral nature of such systems. The magnetic head is a high cost element, while the voice coil system is a much lower cost element. However, in an integral system, if a voice coil element is defective, the entire coarse positioner system, including the relatively expensive head, needs to be replaced.
Another concern with conventional systems is the use of a flexible printed circuit (FPC) routing system that requires locating tabs and corresponding screws for attachment of the locating tabs. The resulting design presents manufacturing assembly issues and increased cost of parts. Further, the tab system provides for an FPC registration on a single edge. This requires additional assembly instructions for the proper routing of the FPC.